Per area options for maphilight

Hi kemayo,

I ve just commit a new functionnality for your very nice plugin maphilight. It gives the opportunity to define specific options for each areas of a map. 

For example, you can now define specific colors for each area. 
If no specific options are defined for an area, default options are used. 

The per area options are implemented this way : 

1- each area should have an optionnal id in HTML code
2- for each area with an id in HTML, you should define specific options for them, in an areas array, wich is include in options area. 

By this way, you should define specific options for all attributes of your plugin. 

Here is an example of code : 

HTML Map Code : 
```
<map name = "map">
  <area id="categorie-1" shape = "poly" coords = "280,437,247,381,426,397,507,395,519,407,548,419,495,436,340,440,341,440" href = "articles/1" />
  <area id="categorie-2" shape = "poly" coords = "151,356,80,450,108,462,247,378" href = "articles/2" />
  <area id="categorie-3" shape = "poly" coords = "247,378,150,354,66,261,83,260,150,294,203,320,235,324" href = "articles/3" />
  <area id="categorie-4" shape = "poly" coords = "239,324,499,304,507,394,427,398,247,379" href = "articles/4" />
  <area id="categorie-5" shape = "poly" coords = "447,144,462,141,489,159,511,126,561,159,560,198,567,257,641,302,668,350,624,390,553,423,522,411,513,355,497,296,465,238,449,206" href = "articles/5" />
  <area id="categorie-6" shape = "poly" coords = "466,243,356,232,283,247,256,313,239,323,343,315,462,305,499,305" href = "articles/6" />
  <area shape = "rect" coords = "649,20,745,49" href = "contact" id="contact"/>
</map>
```

JQuery Code : 

```
$('.map').maphilight({
          fillColor: '000000', 
          areas : {
            'categorie-1' : {
              fillColor: 'ea1c5e'
            },
            'categorie-2' : {
              fillColor: '94dbd8'
            },
            'categorie-3' : {
              fillColor: 'f39094'
            },
            'categorie-4' : {
              fillColor: 'f24ea0'
            },
            'categorie-5' : {
              fillColor: 'ee5343'
            },
            'contact' : {
              neverOn: true
            }
          }
});
```

If you are interessed by this functionnality, i can help you to update the documentation.

Regards,

Hervé.